Manufacturers and those who utilize information handling systems have become interested in utilizing optical fibers for transmitting signals. Optical fibers include a round inner glass core coated with a material having a different index of refraction from that of the core. Light is transmitted along the core and reflected internally by the coating. Optical fibers may be enclosed in a protective sheath either as a single transmission line (a single fiber) or as a bundle of fibers forming an optical cable. A single optical fiber has the potential to provide simultaneous bidirectional communication. As used in information systems today optical fibers are usually connected between optical sub-assemblies which either transmit or receive optical signals. Examples of various means for providing connections between optical fibers and electronic circuitry are illustrated in U.S. Pat. Nos. 4,273,413 (Bendiksen et al), 4,547,039 (Caron et al), 4,647,148 (Katagiri), 4,707,067 (Haberland et al.) and 5,005,939 (Arvanitakis et al.) which are all incorporated herein by reference.
Optical modules include a two-part housing as described in U.S. Pat. No. 5,005,939 (Arvanitakis et al.). The housing provides two receptacle sections for mounting one or more and most commonly, two barrel-shaped optical sub-assemblies. Typically, one optical sub-assembly is a light transmitter for converting an electrical signal into an optical signal and the other is a light receiver for converting the optical signal into an electrical signal. The housing provides for precise alignment of the optical sub-assemblies with optical fibers contained in a suitable plug-in connector. Also within the housing is an electrical interconnect structure, typically of ceramic construction, with electronic circuits connected on the upper surface. The internal interconnect structure includes leads or pins which protrude through apertures out of the housing to connect to an external electrical interconnect structure, typically a printed circuit board, to complete the optical-electrical connection.
In Arvanitakis et al (Supra), one end of each optical sub-assembly with a respective optic cable and from the other end, conductive leads extend axially for electrical connection to an adjacent edge of the internal interconnect structure in the housing. The central axis of each barrel-shaped optical sub-assembly extends parallel to the planer internal interconnect structure. The leads extend from the adjacent ends of the optical sub-assembly substantially above the interconnect structure so the leads are bent into an elbow or S-shape for soldered or welded connection to interconnection pads on the internal interconnect structure which provides electrical connection to the electronic circuit.
Recently, in U.S. Pat. No. 5,005,939 (Arvanitakis), it was proposed as an alternative to such soldering of the optical sub-assembly leads directly to the internal interconnect structure, that a flexible interconnect structure be used to connect between the leads and the conductive pads of the internal interconnect structure. Disclosed was one end of a ribbon cable soldered to the leads of an optical sub-assembly and a distal end of the cable soldered to the conductive pads of the internal interconnect structure. That patent also disclosed that utilizing a flexible ribbon cable would reduce electromagnetic interference and that additional electromagnetic interference/electrostatis discharge (EMI/ESD) protection could be provided by providing a multilayer ribbon cable which included a ground layer.
Materials and processes for manufacturing conventional flexible ribbon cables are well known, for example, U.S. Pat. No. 4,906,803 (Albrechta) and U.S. Pat. No. 4,435,740 (Huckabee et al.), incorporated herein by reference, describe production of a flexible cable including a conductive circuit layer which may be copper and a dielectric layer of polymer such as Kapton.RTM. (E.I. duPont de Nemours and Co. Typically a conductive metal film is coated with a positive or negative photoresist which is exposed to electromagnetic radiation using a mask, cured and otherwise processed to produce a photoresist pattern. The metal film which is not covered by the photoresist is selectively chemically etched to form the conductive circuit layer. The photoresist is then usually removed. Dielectric layers are etched using a similar chemical process or by laser etching/ablation to form windows through the dielectric layer. The dielectric is laminated onto one or both sides of the circuit layer with the windows positioned for interconnection of the cable to leads of electronic components and termination connections to pads on electrical interconnect structures.
U.S. Pat. No. 4,435,740 (Huckabee et al.) describes connections of leads to flexible circuit boards. Usually a conductive land, which is an area of the conductive layer exposed on the surface of the flexible circuit, is proximate to and encircling an aperture through the flexible circuit board. The land is connected to a conductive path in the flexible circuit board. The lead of a component is inserted into the aperture for soldered connection between the land and the lead. The land and lead are usually pre-tinned in order to facilitate mass soldering of multiple leads through respective connection apertures.
Common methods of mass soldering for connecting leads of components to flexible ribbon cables include wave soldering and immersion soldering. For example, U.S. Pat. No. 4,684,056 (Deambrosio), incorporated herein by reference, describes a wave soldering process for connecting components to printed circuit boards. Processes used for wave soldering components to flexible circuit boards are similar except the flexible circuit and electronic component are usually positioned in a rigid carrier for transportation through the solder wave. Alternatively preforms of solder may be positioned for forming joints in a reflow step utilizing an oven for mass soldering.
U.S. Pat. Nos. 3,504,328 (Olsson) and 3,528,173 (Gall) describe eyelets for insertion into holes in a circuit board. The eyelets contain stiff spring tabs which hold a pin or lead in the center of the eyelet to hold components on the board prior to soldering. Gall also discloses terminal sections of conductors at the holes in the circuit boards with portions of the conductor which are bent into the holes by the insertion of the eyelets. U.S. Pat. No. 3,383,648 (Tems) describes a miniature socket with a stiff catch of spring material for holding and electrically connecting a lead without soldering. U.S. Pat. No. 3,022,480 (Tiffany) describes conductor strips with circularly arranged contact fingers which hold contact pins in place for producing multilayer conductor strips. Similarly U.S. Pat. No. 4,859,188 (Neumann) describes slotted disks of spring material for holding wires to connect a stack of printed circuit boards together. U.S. Pat. No. 4,950,173 (Minemura) describes a female connector or socket with springy parts to hold a pin firmly in place during operation. IBM Technical Disclosure Bulletin Vol. 12 No. 3 August 1969 P. 467 describes a spring type electrical connecting device positioned within a printed circuit board hole. The device has spring elements which bear against a plug for interconnecting layers of the printed circuit board. IBM Technical disclosure Bulletin Vol. 6 No. Jan. 8, 1964 P. 87 discloses lands of internal circuit layers of a multilayer circuit board extending into a through hole so that a pin can be inserted into the hole to interconnect the lands.